A meteoroid is a natural fragment
of rock less than 1 km (.6 mi) across that orbits the Sun.

A meteor is the streak of light
caused when a meteoroid enters Earth's atmosphere. Air friction
melts the meteoroid's surface, making it glow white hot. Meteors
also are called shooting stars.

A meteorite is a meteoroid that
survives the fiery passage through the atmosphere and crashes
to Earth. Most meteorites come from asteroids, but a few are
from Mars and the Moon.

How Old are Meteorites?
Every meteorite has three different ages:

1) Absolute age is when
the rock first formed. Most meteorites are 4.5-4.6 billion
years old.

2) Exposure age is the
time the rock spent as a small fragment drifting in space,
exposed to cosmic radiation. For most stony meteorites, this
was less than 50 million years. Irons show a greater range
of ages.

3) Terrestrial age is
the amount of time the meteorite has spent on Earth.

What are Meteorites Made Of?
Minerals. Some of the minerals are the same ones seen in Earth
rocks. Others are not found on Earth at all. But in both cases,
the minerals in meteorites provide clues to the rocks' origins.